【摘要】 针对网络环境中多媒体数据信息的真实性和完整性认证问题,通过分析PDF页面描述操作符的工作机理,给出了一种适用于PDF文档认证的数字水印算法,将PDF文档字符码的特征信息嵌入到文档字符间距中,检测时通过比较PDF文档的水印信息与字符码特征是否一致来判断文档的真伪.实验结果表明,采用该算法实现的水印不仅具有良好的视觉透明性,还有较强的检错及差错定位能力.更多还原

【Abstract】 The growth of networked multimedia systems has brought many advantages in the creation and distribution of digital works. The transparence of data and the ease of manipulating also facilitates unauthorized use, misappropriation and misrepresentation. In this paper, a digital watermarking algorithm is proposed for PDF (Portable Document Format) document authentication, based on a detailed analysis of PDF operators with reference to page description. The watermark, with the features of the PDF character codes, is embedded into the document by modifying the character spaces. The authenticity of a PDF document can be verified by comparing the watermark with the features of character codes. The experimental results demonstrate that the watermarked PDF document possesses good perceptual transparence, and that the proposed algorithm can detect any character change at the PDF document at the block level.更多还原